The present invention relates to thin liquid crystal display devices.
Typically, a liquid crystal display device 5 includes a liquid crystal display panel in which an opposing pair of substrates sandwiches a display material such as a liquid crystal, a circuit board for driving the display panel, an edge lighting unit disposed behind the display panel, and a frame covering these components. The edge lighting unit includes a light guiding board, a lamp disposed on each lateral side of the board, and a holder for holding each lamp. Conventional liquid crystal display devices are shown in FIGS. 10 and 11 and include frames 1a and 1b, a liquid crystal display panel 2, circuit boards 3a and 3b, a light guiding board 4, lamps 5a and 5b, lamp holders 10a and 10b, and a lamp housing 11.
As shown in FIG. 10, one conventional liquid crystal display device includes a light guiding board 4 comprising one board on respective lateral sides of which are disposed the lamps 5a and 5b and lamp holders 10a and 10b for holding the corresponding lamps 5a and 5b, and outer frames 1a and 1b that sandwich and cover these components, together with a liquid crystal display panel 2 and circuit boards 3a and 3b. Alternatively, as shown in FIG. 11, another conventional liquid crystal display device includes separably assembled, using a fastening member 100 such as a screw, a lighting unit A including a lamp housing 11 for holding a light guiding board 4 and lamps 5a and 5b and a liquid crystal display panel section B including a liquid crystal display panel 2, circuit boards 3a and 3b, and outer frames 1a and 1b that sandwich and hold the panel 2 and circuit boards 3a and 3b.
When a liquid crystal display device is used in individual display devices, such as an OHP (Over Head Projector) and personal computer, the lighting means needs to be replaced with a suitable one. However, in conventional liquid crystal display devices employing the described structures, the frames 1a and 1b must be first removed to separate the lighting unit section A or the light guiding board 4 from the liquid crystal display panel section B. This process entails cumbersome operations in disassembly and assembly.
In the conventional liquid crystal display device shown in FIG. 10, the monolithic light guiding board 4 together with the liquid crystal display panel 2 and the like are covered by the frames 1a and 1b. Accordingly, to remove or mount only the lamps or light guiding board 4, they must be detached from the lamp holders 10a and 10b after removal of the frames 1a and 1b. This process not only is cumbersome but also degrades the reliability of the device since the circuit boards 3a and 3b are exposed in the conventional liquid crystal display device shown in FIG. 11, on the other hand, the lighting unit and the liquid crystal display panel section are readily separable and the problem associated with the other conventional device does not arise. Nevertheless, these sections each have an element for fastening them together, enlarging the dimensions of their outer forms.
Further, with the foregoing edge light type lighting unit, light from the lamps on opposite sides of the light guiding board 4 propagate toward the center of the light guiding board 4. Only light that is deflected upwardly, as viewed in the drawing, by reflection or diffusion means (not shown) on the upper or lower side of the light guiding board 4 is utilized to illuminate the liquid crystal display panel 2, resulting in insufficient utilization of light.
Still further, since the light guiding board 4 is relatively heavy, it is difficult to position the board 4 precisely during its mounting, and significant labor is needed for handling the board 4.